Viscose solutions for making flame retardant rayon



VISCOSE SOLUTIONS FOR MAKING FLAME RETARDANT RAYON Joseph W. Schappel, Morton, Pa., and Arthur I. Bates,

Wilmington, Del., assignors, by mesne assignments, to FMC Corporation, San Jose, Calif., a corporation of Delaware No Drawing. Filed Dec. 19, 1962, Ser. No. 245,653

2 Claims. (Cl. 106-165) The present invention relates to viscose solutions for the production of flame retardant shaped bodies, such as filaments and fibers.

Conventional procedures for imparting flame retardant properties to shaped bodies of regenerated cellulose involve impregnating or coating of regenerated cellulose filaments, fibers or *fabrics formed therefrom with a suitable flame retardant composition followed by drying. Such flame retardant finishes often alter the hand or other physical properties of the treated materials and, more important, are generally fugitive and are thus readily removed by laundering or leaching in water.

It is an object of this invent-ion to provide viscose solutions which are capable of being coagulated to form afterglow-resistant and fire-retardant regenerated cellulose structures.

It is a further object of this invention to provide viscose solutions for making afterglow-resistant and flame-retardant regenerated cellulose filaments, fibers, "fabrics and like structures which retain their afterglow-resistant and flameretardant properties after a considerable number of launderings in an aqueous medium.

Still further objects and advantages of the present invention will appear in the following detailed description and claims.

In accordance with the present invention, afterglowresistant and flame-retardant regenerated cellulose filaments, fibers and other shaped products are formed from a viscose containing brominated triallyl phosphate, and more particularly the fully brominated material; namely, tri-(2,3 dibromopropyl) phosphate. Aside from the incorporation of the tri-(2,3 dibromopropyl) phosphate, the viscose and the spinning bath employed in making the shaped regenerated cellulose products of the present invention may be of conventional or known composition. The aging and spinnability of the viscose is apparently not aifected by the presence of the tri-(2,3 dibromopropyl) phosphate which may be added to and mixed with the viscose well in advance of spinning operations, or which may be injected into the viscose at the spinning machine, with or without being first dissolved in an alcohol or prepared as a water emulsion.

The afterglow-resistant and flame-retardant properties of the resulting regenerated cellulose shaped products will, in general, vary with the amount of tri-(2,3 dibromopropyl) phosphate initially added to the viscose. To provide regenerated cellulose shaped products having selfextinguishing properties, not less than about of the tri-( 2,3 dibromopropyl) phosphate, based upon the weight of the cellulose, should be incorporated into the viscose. Regenerated cellulose filaments and fibers which are not self-extinguishing but which do exhibit some flame retardant properties may be made by incorporating as little as 2% of the tri-(2,3 dibromopropyl) phosphate, based upon the weight of the cellulose. From the standpoint of economy, and to minimize a loss in the tenacity of the finished filaments and fibers, as more fully discussed hereitented August 16, 1966 after, the amount of tri-(2,3 dibromopropyl) phosphate added to the viscose should perhaps not exceed more than 30% to 40%, again based upon the weight of the cellulose.

When incorporated into a conventional viscose, the tri-(2,3 dibromopropyl) phosphate disperses as an emulsified organic oil in a very finely divided condition. Generally, as much as to of the tri-(2,3 dibromo propyl) phosphate originally added to the viscose is retained by the finished regenerated cellulose filaments or fibers and appears as embedded oil particles which neither allect the hand, color, luster, dyeability nor launderability of such products.

The terms afterglow resistant and fire-retardant as used in the description and claims is intended to designate a structure which is resistant to the propagation of flame across its surface after the igniting flame has been removed (self-extinguishing) and which is also resistant to smoldering or the formation of a non-flaming combustion which manifests itself as a red glow.

As heretofore mentioned the viscose may be of conventional composition, containing from about 4% to about 10% cellulose, about 4% to about 8% caustic soda and from about 30% to about 50% carbon disulfide; based upon the weight of the cellulose. The modified viscose, that is, the viscose containing the tri-(2,3 dibromopropyl) phosphate, may have any desired salt test at the time of spinning or extrusion. If desired, the viscose may contain other known additives so as to improve the physical properties of the regenerated cellulose products and to alter the fine structure of the cellulose as is commonly practiced in the industry.

The viscose is formed in the conventional manner and either during its preparation or just prior to spinning may be further modified by the addition of a viscose or coagulation modifier. A large number of modifiers are known and are in use in the production of the various types of viscose rayon. These modifiers include polyoxyalkylene glycols such as polyoxyethylene glycols, polyoxypropylene glycols and block copolymers of propylene and ethylene oxides; various amines including monoamines, diamines and polyamines such as diethylamine, dimethylamine, ethylene diamine and diethylene triamine; reaction products ozt alkylene oxides with fatty acids, fatty alcohols, fatty amines, aromatic acids, aromatic alcohols, aromatic amines, partial esters of fatty acids and polyhydric alcohols such as reaction products of ethylene oxide with lauryl alcohol, phenol, lauryl amine, glycerol monostearate, etc.; quaternary ammonium compounds and the like. The amount of modifier may vary from about 2% to about 5%, based on the weight of the cellulose.

When using conventional viscose modifiers or coagulation modifiers, it is preferred to utilize a combination of modifiers such as a monoamine and a polyoxyalkylene glycol or a polyoxyalkylene glycol ether of an aromatic alcohol or of a polyhydric alcohol wherein the glycol or ether has a molecular weight of between about 600 and about 4000 to 6000; for example, dimethylamine and a polyoxyethylene glycol or a polyethylene glycol ether of phenol or of sorbitol having a molecular weight within the stated range. In the use of the combination, the rnonoamine is added in an amount of from about 1.5% to 3.5% and the glycol or ether in an amount of from about 1% to 3%, both proportions being based upon the Weight of the cellulose.

The spinning bath employed in coagulating the modified viscose may also be of conventional composition and 3 may include from about 5% to sulfuric acid, from about 3% to zinc sulfate, and from about 10% to sodium sulfate, preferably from 4% to 9% zinc sulfate and 15% to 22% sodium sulfate. Other metal sulfates, such as iron, manganese, nickel and the like may be present and may replace some of the zinc sulfate. The temperature of the spinning bath may vary from 25 C. to about 80 C., and is preferably between C. and 70 C. to insure that the resulting regenerated cellulose filaments and fibers possess good physical properties, and especially tensile strength which sutfers somewhat as compared with conventional filaments, as will be more apparent hereafter.

From the spinning bath, and prior to washing, the filaments may be passed through a stretch bath and stretched from about 25% to 145% during their passage through the bath. The stretch bath is maintained at a temperature between about 85 C. and 100 C. and may be a hot water bath or may contain 1% to 5% sulfuric acid with or without from about 1% to 4% zinc sulfate and from about 4% to 7% sodium sulfate.

The filaments are then subjected to the usual aftertreatments which include washing and desulfurizing and, if desired, bleaching either before or after collection of the filaments. The filaments may or may not be provided with a yarn finish before being dried.

The regenerated cellulose shaped products, such as filaments and fibers, formed in accordance with the present invention may be converted into fabrics using conventional processes and equipment. Preferably, such filaments and fibers are used alone or, at most, blended with only a negligible amount of conventional filaments or fibers when it is desired to preserve the full benefit of their afterglow-resistant and flame-retardant properties.

The invention may be further illustrated by reference to the preparation of regenerated cellulose filaments from a viscose containing about 5.0% cellulose, about 6.0% caustic soda, and having a total carbon disulfide content of about 38.0%, based on the weight of the cellulose. The viscose solution was prepared by xanthating alkali cellulose by the introduction of 38.0% carbon disulfide based on the weight of the cellulose and churning for about 2 /2 hours. The cellulose xanthate was then dissolved in caustic soda solution. About 2.6% dimethylamine and 2.6% of a polyoxyethylene glycol having a molecular weight of about 1500 was added to and mixed with the viscose, along with 15% tri-(2,3 dibromopropyl) phosphate, based on the weight of cellulose. The viscose was then allowed to ripen and had a salt test of 8.5.

As a control, a second viscose was prepared which was substantially the same as that described above with the exception that no tri-(2,3 dibromopropyl) phosphate was added.

Both the above described viscose solutions were then extruded through individual spinnerets to form 600 dinier, 400 filament yarns at a rate of about 28 meters per minute. The coagulating and regenerating bath was maintained at a temperature of about C. and contained 6.8% sulfuric acid, 5.0% zinc sulfate and 17.5% sodium sulfate. The yarns were stretched about 110% while passing through a cascade bath (93 C.) of 5% acid. The yarns were passed through the conventional rayon processing cycle, including a hypochlorite bleach bath, collected in spinning boxes, washed free of acids and salts and dried. Spinning of the modified viscose was completely satisfactory with no evidence of filter clogging or jet slubbing. The processed yarns, in both instances, were white and soft.

A fabric was woven having afterglow-resistant and flame-retardant filaments, which were formed as described above, in both warp and filling, and a similar fabric was formed using the control filaments. Both yarns processed satisfactorily through warping and weaving, and the fabrics processed without difiiculty through jig scouring and frame drying. Additionally, both fabrics appeared to possess substantially the same dyeing properties. The physical properties of the woven control fabric and the fabric formed of the afterglow-resistant and flame-retardant filaments, designated as Fabric X, were as follows:

Property Control Fabric X Grab Strength (ll)s.):

Cond.

80. 3 73, 4 l i l 78. 4 M. 0 Skill-Flex S. 200. 8 3150. 0 Shrinkage 140 F.:

1st wash- 15. 50 14. 00 Fill. 20 1. 00 Flannnabilit AATCC 3349 i nite (Warp and Fill) 2 DNI DNI Time to Ignite, Seconds- \Vnrp. 6 4 Fill 5 4 ll xtin; elf-Warp and Fill N0 3 3 05 Seconds to burn 5 \Vnrp 24 Fill 28 American Association of Textile Chemists and Colorists Standard Test Method.

2 Did not ignite in one second.

5 Also exhibited no afterglow.

The above described woven fabrics were also subjected to sunshine exposure tests wherein uncovered samples and samples covered with glass were exposed to sunlight for different periods. The glass employed in this test was ordinary window glass of good quality having a thickness of 2.5 mm. The test results were as follows:

50 HOUR SAMPLES .823 Total 1 Ravel 5 UVSH l Lang- Lang- Strip leys 2 leys Strength Control Under Glass..- 50. 0 3, 468 4, 779 143. 3 Fabric X Under (31:155.. 50. 0 3, 468 4, 779 128. .2 (ontrol Direct. E\posr1re. 52. 9 3, 900 5,455 158. 5 Fabric X Direct Exposure... 52. 9 3, 090 5, 455 130. 3

ll OUR SAMPLES 200 HOUR SAMPLES 200 14,033 17, 007 100. 0 Fabric 57. Under (1 t 200 14,033 17,007 130. 0 Control Direct Exposure. 200 14, 534 18,701 167. 0 Fabric X Direct Exposure... 200 14, 534 18, 761 118.0

1 UVSll-Total amount of sun hours accumulated during exposure cycle or Ultra Violet. Sun liours.

3 Langley-one grain calorie per square centimeter or 3.00 Btufs per square foot. The total Lnnglcys are the number oi Lungleys aocurnnlated over an entire test, while the UV Langley is designated as the number of Lungleys accumulated when the solar radiation is at or above .823 Langleys.

3 Pounds to break.

While the sunshine exposure tests indicate that fabrics made of filaments formed from viscose solutions of the present invention exhibit some loss in tenacity, such loss is comparatively slight and offset by the afterglow-resistant and flame-retardant properties incorporated into the finished fabric. As heretofore mentioned, such loss in tenacity can be minimized by employing the smallest amount of tri-(2,3 dibromopropyl) phosphate necessary for producing the desired results.

3,266,918 5 We claim: about 10% to 40% by weight, based on said cellulose, 1. A viscose solution containing from 4% to 10% of tri-(2,3 dibromopropyl) phosphate. by Weight of cellulose in which is incorporated from about 2% to 40%, by weight, based on said cellulose, References Cited by the Examiner of tri-(2,3 dibrornopropyl) phosphate sufficient to im- 5 UNITED STATES PATENTS part fire-retardant properties to a dry regenerated cellu- 2 574,515 11 1951 Walter et 1 1()6 .177 loose material formed from said viscose solution by acid- 2,816,004 12/1957 .R i t 1, 106 165 ification.

2. A viscose solution containing from 4% to 10% by ALEXANDER KEL, Primary Examiner. weight of cellulose and in which is incorporated from 10 L. HAYES, Assistant Examiner. 

